The effects of calcium fertilizer on anthracnose and Rhizopus tuber rot of yam

Abstract

Yam (Dioscorea spp) production is beset in the field and in storage by major fungal pathogens, namely Colletotrichum gloeosporioides that causes anthracnose in the field, and Rhizopus stolonifer that causes tuber rot in storage. Alternative control measures are imperative as conventional control of these pathogens is either ineffective or detrimental. This study investigated the effects of calcium fertilizer on the incidence and severity of anthracnose and Rhizopus rot of yam. Calcium nitrate fertilizer was applied to soils naturally infected with C. gloeosporioides, at the rates of 0, 3, and 4kg ha-1. D. rotundata variety Efuru was planted. The treatments were arranged in a randomized complete block design with three replicates. Anthracnose disease rating relied on natural endemic infection in the field, while inoculation of harvested yam tubers was carried out using R. stolonifer. There was no significant effect of calcium amendment of the soil on anthracnose severity in D. rotundata or on the agronomic parameters. D. rotundata tubers treated with 3 and 4kg ha-1 calcium soil amendments had reduced infection by R. stolonifer in storage compared to the control treatments. The study concluded that calcium applied to the soil had reduced storage losses by R. stolonifer in D. rotundata but had no influence on anthracnose severity in the field. Therefore, 3kg ha-1 of calcium nitrate applied to the soil can be used to improve D. rotundata tuber resistance to R. stolonifer, and is recommended for high-quality tuber storage.